Exhaust gas treatment devices in the exhaust systems of internal combustion engines that propel motor vehicles prevent significant amounts of undesired products of combustion from being emitted to the surrounding atmosphere. For assuring full effectiveness whatever after-treatment device or devices is or are present in an exhaust system, it is important for integrity of the exhaust system to be assured.
The present invention is directed to a system that includes devices for placement in an engine exhaust system to obtain measurements of certain physical characteristics of exhaust gas flowing through the exhaust system and processing equipment for processing data related to exhaust gas flow past those devices to yield data representing the mass flow of exhaust gas through the exhaust system.
The invention further relates to processing the exhaust mass flow data with data representing mass flow introduced into engine combustion chambers for combustion to yield data indicative of any leakage from the exhaust system upstream of the devices placed in the exhaust system.
The invention still further relates to obtaining the exhaust mass flow data both upstream and downstream of an exhaust gas treatment device and processing the obtained data to yield data indicative of any leakage from the exhaust gas treatment device.
By monitoring for leakage in such ways, compliance with any relevant laws and/or regulations can be proven. Alternatively, detection of leakage can be signaled, enabling early correction of a leak.
Principles of the invention can be embodied in an engine by the exposure of two devices to exhaust gas flow, in conjunction with suitable algorithms in on-board processing apparatus, such as apparatus present in a processor-based engine control system.
One of the two devices comprises a sensor having the capability for accurately sensing exhaust gas temperature. The other device comprises an electric heater having the capability to be heated to a temperature in excess of exhaust gas temperature. By using an existing exhaust gas sensor as the other device, the invention can be cost-effectively implemented in a motor vehicle.
Execution of an algorithm that processes temperature data provided by the sensor and power data representing power required to maintain heater temperature yields data representing mass flow through the exhaust system past the temperature sensor and the electric heater.
Execution of a further algorithm that processes the exhaust mass flow data and data obtained from mass flow measuring apparatus that measures mass flow entering the engine for combustion yields data representing any leakage in the exhaust system occurring upstream of the exhaust system sensor and heater.
Principles of the invention can also be embodied in an engine by the exposure of a first pair of the two devices to exhaust gas flow upstream of an exhaust gas treatment device and a second pair of the two devices downstream of the exhaust gas treatment device, in conjunction with suitable algorithms in on-board processing apparatus, and processing data obtained through use of the four devices to yield data representing any leakage from the exhaust gas treatment device.
Accordingly, one general aspect of the present invention relates to a method of measuring mass flow of exhaust gas through an exhaust system of an internal combustion engine. The method comprises developing temperature data representing temperature of exhaust gas flowing past a temperature sensor disposed in temperature sensing relation to the exhaust gas flow, and developing power data representing power required to heat an electric heater disposed in heat exchange relation with the exhaust gas flow to a temperature in excess of temperature of exhaust gas flow past the heater. The temperature data and the power data are then processed according to an algorithm for yielding data representing mass flow of exhaust gas.
Another general aspect relates to an engine that embodies the method just described.
Still another general aspect of the invention relates to a method of measuring leakage of exhaust gas from an exhaust system of an internal combustion engine. The method comprises developing temperature data representing temperature of exhaust gas flowing past a temperature sensor disposed in temperature sensing relation to the exhaust gas flow, and developing power data representing power required to heat an electric heater disposed in heat exchange relation with the exhaust gas flow to a temperature in excess of temperature of exhaust gas flow past the heater. A processor processes the temperature data, the power data, and data representing mass flow through the engine upstream of the temperature sensor and heater according to an algorithm for yielding data representing the difference between mass flow of exhaust gas past the temperature sensor and heater and mass flow upstream of the temperature sensor and heater.
Another general aspect relates to an engine that embodies the method just described.
The foregoing, along with further aspects, features, and advantages of the invention, will be seen in this disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, briefly described below, and contains a detailed description that will make reference to those drawings.